You can try out Join Texts on our staging instance.
It works very much like a Rollup, but you can also specify a separator. If you use just a newline as the separator you won’t see it in the Data Editor, but it’ll be there if you save the column to a sheet.
Writing the array column to the spreadsheet is not just a “restriction” we can remove. Google Sheets don’t support arrays, so we’d have to decide how to write them. For example, how to separate individual values, which Join Texts lets you do 